The handover (or handoff) procedure is a means to continue a call when a user terminal crosses the border of one cell to another. In a cellular network, a cell typically has several neighbouring cells. The basic concept of handover is that when a user terminal moves from the coverage area of one cell to another, a new connection to the target cell is set up and the connection to the old cell may be released.
In hard handovers, the main problem is the downlink user data interruption time caused by delays in signalling messages and a round-trip delay between the terminal and physical channel-switching device on the network side.